Germanium dithiophosphate

ABSTRACT

A hydrocarbon is catalytically cracked employing a cracking catalyst contacted with a treating agent selected from germanium and germanium compounds.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of copending application Ser. No. 449,319, filedDec. 13, 1982, which is a divisional of Ser. No. 276,402, filed June 22,1981, now U.S. Pat. No. 4,386,015, which in turn is a divisional ofapplication Ser. No. 139,483, filed Apr. 11, 1980, now U.S. Pat. No.4,334,979.

BACKGROUND OF THE INVENTION

This invention relates to a process for cracking a hydrocarbonfeedstock. In another aspect, the invention relates to a process forpassivating contaminants on a cracking catalyst. In still anotheraspect, the invention relates to a cracking catalyst.

Contaminants, for example, nickel, vanadium and iron are found insignificant concentrations in heavy oil fractions and lower qualitycrude oil. These contaminants have a poisoning effect on the expensivecracking catalysts employed to convert crude oil into gasoline and othervaluable petroleum products, frequently making exploitation of theseoils economically unattractive. Unfortunately, because of limitedsupplies of oils containing low levels of contaminants, it is sometimesnecessary to employ the metals-contaminated oils in catalytic crackingprocesses.

The contaminants found in feedstocks to cracking processes becomedeposited on the cracking catalyst. The deposition on the catalyst of,for example, nickel, vanadium and iron, causes a decrease in theactivity of the cracking catalyst to convert the hydrocarbon feedstockinto cracked products, including gasoline. The selectivity of thecracking catalyst for cracking the feedstock into gasoline, asmanifested by the portion of cracked products comprising gasoline, isalso decreased. The production of undesirable products, for example,hydrogen and methane, which must be compressed, necessitating additionalequipment; and coke, which is deposited on the catalyst and must beburned off, requiring additional equipment and "off-time" during whichthe catalyst is not employed for cracking, is significantly increased.

Because of these problems, the industry usually replaces crackingcatalysts contaminated by more than about 3,000 parts per million (ppm)of vanadium equivalents of vanadium and nickel, defined as the sum ofthe parts by weight of vanadium and four times the parts by weight ofnickel in one million parts by weight of contaminated cracking catalyst.This level of contamination is rapidly reached when cracking heavilycontaminated feedstocks. There is thus a need for a cracking processsuitable for use with contaminated feedstocks and contaminated crackingcatalysts. There is also a need for a cracking catalyst which is onlyminimally adversely affected by deposits thereon of contaminantsselected from nickel, vanadium and iron. There is also a need for aprocess of treating a contaminated cracking catalyst to increase itsactivity for conversion and selectivity for producing gasoline and todecrease its selectivity for producing undesirable products, forexample, hydrogen and coke.

OBJECTS OF THE INVENTION

It is thus an object of the present invention to provide an improvedcatalytic cracking process well adapted for cracking metals containingfeedstocks.

Another object of this invention is to provide a process for thepassivation of contaminants deposited on a cracking catalyst and thusreduce their adverse effects on the cracking process.

Another object of the invention is to provide a process for at leastpartially restoring used cracking catalyst so that it can continue to beeconomically employed in a catalytic cracking process.

Another object of this invention is to provide a modified crackingcatalyst which has a low susceptibility to metals poisoning.

Another object of this invention is to provide a cracking catalyst whichprovides high yields and selectivity for gasoline or higher-boilinghydrocarbon fuel and remains highly selective as contaminants becomedeposited thereon.

Other aspects, objects and the several advantages of the invention willbe readily apparent to one skilled in the art from the followingdisclosure and the appended claims.

SUMMARY OF THE INVENTION

In accordance with the invention, a cracking catalyst compositioncomprises a cracking catalyst in combination with a treating agentselected from germanium and germanium compounds.

Further, according to the invention, a hydrocarbon feedstock iscatalytically cracked employing the above-described catalystcomposition.

Still further, according to the invention, at least one metal selectedfrom nickel, vanadium and iron in contact with a cracking catalyst ispassivated by contacting the cracking catalyst with a treating agentselected from germanium and germanium compounds.

Still further, according to the invention, a used cracking catalystcontaining at least 3,000 ppm vanadium equivalents is at least partiallyrestored upon contact with a treating agent selected from germanium andgermanium compounds.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that the adverse effects of metals, for example,the adverse effects caused by nickel, vanadium and iron on a crackingcatalyst can be precluded or reduced by contacting the cracking catalystwith a treating agent selected from germanium and germanium compounds.The treating agent can be selected from elemental germanium, inorganicgermanium compounds, organic germanium compounds, and mixtures orsolutions having at least one germanium treating agent. Most anygermanium-containing composition is believed to be suitable. Examples ofinorganic germanium compounds which can be employed include the halides,nitrides, hydrides, oxides, sulfides, selenides, tellurides, imides,sulfates, and phosphates of germanium in any of its valence states andmixtures of any two or more of such compounds. Germanium containingmaterials, for example, argyrodite and canfieldite, and germaniumcontaining impure materials, for example, those recovered during theprocess of other metals, such as, zinc germanate and magnesium germanateare also believed to be suitable sources of germanium. Examples oforganic germanium compounds which can be employed include germaniumcompounds of the formula ##STR1## wherein R₁, R₂, R₃ and R₄ areindependently selected from the group consisting of hydrogen, halogen,hydrocarbyl and oxyhydrocarbyl. The above formula is intended to includegermanium compounds wherein two R_(x) groups represent the same radical,as in germanium complexes, for example, germanium citrate. Thehydrocarbyl and oxyhydrocarbyl radicals can have, for example, from 1-20carbon atoms and can be substituted, for example, with halogen,nitrogen, phosphorus or sulfur. Exemplary hydrocarbyl and oxyhydrocarbylradicals are alkyl, alkenyl, cycloalkyl, aryl, and combinations thereof,for example, alkylaryl or alkylcycloalkyl. Thus, germanium compoundssuch as tetrabutylgermanium, germanium tetrabutoxide, tetraphenylgermanium, germanium tetraphenoxide, germanium tetrakis(thiophenoxide),triphenylgermanium thiobenzoate, or diphenyldibromogermanium can beemployed in the present invention.

The presently preferred treating agents are the germanium salts ofhydrocarbyl-phosphoric and hydrocarbyl-thiophosphoric acids. Thecompositions are conveniently represented by the formula ##STR2##wherein R is hydrocarbyl having 1-20 carbon atoms and X is independentlyselected from oxygen and sulfur. Preferably, R is alkyl having from 1 toabout 6 carbon atoms because of commercial availability of suitablesynthesis materials, the oil solubilities of the represented compositionwherein R has 1-6 carbon atoms, and because compositions having between1 and about 6 carbon atoms in the R group have been tested with goodresults. These compositions can be formed, for example, by the doubledecomposition reaction between a germanium tetrahalide, for example,germanium tetrachloride, and a potassium salt of a selectedhydrocarbylphosphoric or hydrocarbyl-thiophosphoric acid, for example,potassium di-n-propylphosphorodithioate. The desired germanium salt canbe separated from the potassium chloride by-product by methods known inthe art. The organic moieties can be alkyl, aryl, cycloalkyl, alkylaryl,arylalkyl, alkenyl, alkenyl-aryl and the like in nature. Compositionsrepresented by the formula ##STR3## wherein R is as defined before arepreferred because of ease of synthesis. Germaniumtetrakis(di-n-propylphosphorodithioate) is the treating agent presentlypreferred, because it has been employed with good results.

Mixtures or solutions having one or more germanium treating agents arealso operable. In addition to at least one germanium treating agent,mixtures or solutions employed can also desirably contain elements orcompositions containing elements selected from Groups IVA, VA and VIA ofthe periodic table as published in the Handbook of Chemistry andPhysics, Chemical Rubber Company, 45th Ed., 1964, p. B-2. Thus,compounds, solutions and mixtures which contain elements selected fromthe group consisting of tin, phosphorous, antimony, bismuth, sulfur,selenium and tellurium can be employed in addition to germanium treatingagents to at least partially preclude or mitigate the undesirableeffects of metals on the cracking catalyst. Sulfides, selenides andtellurides of tin, antimony and bismuth and sulfates, phosphates andthiophosphates of tin, antimony and bismuth as well as hydrocarbyl andoxyhydrocarbyl derivatives of these elements and compounds are exemplaryof non-germanium compounds which can be advantageously employed inconjunction with the selected germanium treating agent. The presentlypreferred treating agent of this class is a mixture of germaniumtetrakis(di-n-propylphosphorodithioate) and antimonytris(di-n-propylphosphorodithioate) because it has been employed withgood results and is oil-soluble. The preferred mixture has a weightratio of germanium to antimony of between about 1:100 to about 100:1,more preferably between about 1:10 to about 1:1, because a mixturewithin this range has been employed with good results.

Because the main purpose of germanium on the cracking catalyst materialis to prevent or mitigate the otherwise (without germanium) occurringundesirable effects of contaminating metals, in particular the increasedhydrogen and coke production and the reduced yield of gasoline orhigher-boiling hydrocarbon fuels such as kerosene, diesel fuel andburning oils caused by these contaminating metals, the sources ofgermanium utilized and incorporated into or onto the cracking catalystshould be essentially free of contaminating metals. Accordingly, it isdesirable that the germanium sources should essentially contain nonickel, no vanadium and no iron.

The treating agent can be contacted with used cracking catalyst, unusedcracking catalyst, or a mixture thereof in accordance with the presentinvention and prior to, and/or during the use of the catalyst. Use ofthe treating agent with used cracking catalyst increases catalystactivity, increases catalyst selectivity for gasoline production, andsurprisingly, decreases the production of hydrogen and the production ofcoke. Likewise, use of the treating agent with new cracking catalystmaintains high activity and selectivity and low hydrogen and cokeproduction. The term "cracking catalyst" as used herein refers to eithernew or used zeolite-containing cracking catalyst materials which areuseful for cracking hydrocarbons in the absence of added hydrogen.

The cracking catalyst advantageously treated in accordance with thepresent invention can be any zeolite-containing cracking catalystsuitable for catalytic cracking of hydrocarbons which is susceptible tobecoming deleteriously affected by the presence of one or more of themetals of nickel, vanadium and iron. Such catalysts are often used tocatalytically crack hydrocarbons boiling above 400° F. (204° C.) for theproduction of gasoline, motor fuel blending components and lightdistillates. Some of the more common cracking catalysts generallycontain silica or silica-alumina, such materials being associated withthe zeolitic component. These zeolitic materials can be naturallyoccurring, or they can be manufactured by methods well known in the art.The zeolitic materials are often ion exchanged with metallic ions and/orammonium ions to improve the activity and/or selectivity of thecatalyst. Zeolite-modified silica-alumina catalysts are particularlyapplicable in this invention, especially those silica-alumina catalystscomprised of from about 1 to about 60% zeolitic material. Examples ofcracking catalysts useful in the present invention include, for example,hydrocarbon cracking catalysts obtained by admixing an inorganic oxidegel with an aluminosilicate and aluminosilicate compositions which arestrongly acidic as a result of treatment with a fluid medium containingat least one rare earth metal cation and a hydrogen ion, or ion capableof conversion to a hydrogen ion. The catalytic cracking materials canvary widely in pore volume and surface area. Generally, however, theunused cracking catalyst will have a pore volume in the range of about0.1 to about 1 mL/g. The surface area of this unused catalytic crackingmaterial generally will be in the range of about 50 to about 500 m² /g.Preferably, the cracking catalyst is suitable for use in a fluidcatalytic cracking process. In a fluid catalytic cracking process, theunused catalytic cracking material employed will generally be inparticulate form having a particle size principally within the range ofabout 10 to about 200 microns. The preferred cracking catalysts arecommonly referred to as FCC catalysts, and are well known by thoseskilled in the art.

The unused catalytic cracking material will often exhibit concentrationsof nickel vanadium, and iron within the following ranges, although forbest results it is preferred that the unused catalytic cracking materialcontain essentially no nickel or vanadium:

    ______________________________________                                        nickel          0 to 0.02 weight percent                                      vanadium        0 to 0.06 weight percent                                      iron            0 to 0.8 weight percent.                                      ______________________________________                                    

The weight percentages in this table relate to the total weight of theunused catalytic cracking material including the metals nickel, vanadiumand iron, but excluding the added germanium treating agent. The contentsof these metals on the cracking catalyst can be determined by standardmethods well known in the art, e.g., by atomic absorption spectroscopyor by X-ray fluorescence spectroscopy.

During use, the cracking catalysts become slowly deactivated fromaccumulations thereon of contaminants from the hydrocarbon feedstock.The accumulated contaminants also adversely affect the selectivity ofthe cracking catalyst for cracking the feedstock to desirable products.The cracking catalyst produces more hydrogen and coke, and lessgasoline, from the hydrocarbon feedstock. The contaminants whichaccumulate on the cracking catalyst include nickel, vanadium and iron,although a large portion of the iron detected during analysis of usedcracking catalyst is so-called "tramp iron", and has as its origineroded ferrous equipment, rather than the hydrocarbon feedstock. Trampiron is believed to have little effect on the cracking ability of thecatalyst. Because it is difficult to distinguish tramp iron on thecatalyst from catalytically active iron, the degree to which thecatalyst is contaminated is often assessed in terms of vanadiumequivalents of contaminating metals, which is a measure of theaccumulations of only vanadium and nickel. The vanadium equivalents ofcontaminants on the cracking catalyst is expressed herein in parts permillion (ppm) and is the sum of the parts by weight of vanadium and fourtimes parts by weight of the nickel on one million parts by weight ofcontaminated cracking catalyst.

The activity and selectivity of untreated cracking catalyst declines asmetals become deposited on the catalyst from the feedstock. Usually theactivity and selectivity of the cracking catalyst have so declined bythe deposit thereon of about 3000 vanadium equivalents that it isuneconomical to continue its employment for cracking. However, theobservable improvement in the activity and selectivity of the crackingcatalyst upon treatment with the germanium containing treating agent inaccordance with the present invention increases with increasing levelsof contaminants on the cracking catalyst. Thus, in accordance with thepresent invention, catalysts having deposited thereon in excess of 3,000ppm of vanadium equivalents generally can be regenerated to the pointwhere they can be economically employed in a cracking process, forexample, the cracking of heavy oils. In one aspect of the presentinvention, it is preferable that the cracking catalyst to be treated bea used catalyst having deposited thereon at least 3,000 ppm vanadiumequivalents thereby reacting a deactivated cracking catalyst that mightotherwise have to be disposed of. When employed in this manner,treatment of the cracking catalyst in accordance with the invention iseffective to at least partially reactivate deactivated crackingcatalysts containing 6,000, 10,000 and even 20,000 and beyond vanadiumequivalents.

The amount of treating agent contacted with the cracking catalyst can beselected over a wide range. Generally, the amount of treating agentemployed will be sufficient to impart to the cracking catalyst a"passivating amount" of germanium. By "passivating amount" is meant anamount of treating agent effective to mitigate an adverse effect causedby the presence of nickel, vanadium or iron in contact with the crackingcatalyst. A passivating amount of germanium treating agent is dependent,at least to some extent, on the amounts and activities of thecontaminants deposited or expected to be deposited on the crackingcatalyst. The activity of a particular contaminant to detrimentallyaffect the cracking process is generally dependent on factors such asits residence time on the catalyst and its identity. In addition,certain combinations of contaminants may cooperate synergistically tocause adverse effects. The amount of germanium treating agent necessaryto passivate a given amount of metals on an equilibrium crackingcatalyst can be approximated in terms of the vanadium equivalents ofcontaminating metals deposited on the catalyst for many fluid catalyticcracking operations. Expressed in these terms, a passivating amount ofgermanium treating agent, expressed as the ratio between the elementalweight of germanium to vanadium equivalents on the cracking catalyst, isgenerally in the range of from about 1:5000 to about 5:1, morepreferably from about 1:1000 to about 1:1, and most preferably fromabout 1:500 to about 1:5. The broad range is believed to be the generalrange in which the present invention would be employed for mostequilibrium catalysts, the intermediate range is believed to be therange in which the invention would be more often employed and thenarrowest range is provided as a range which has provided good results.

The amount of germanium on the treated cracking catalyst will generallybe from 0.0001 to about 4 parts by weight germanium per 100 parts byweight of treated cracking catalyst, i.e., the weight of crackingcatalyst with the treating agent and contaminants deposited thereon. Forcracking catalysts in which germanium atoms have been substituted forthe conventionally employed silicon atoms, all weight ranges used hereinrefer to the weight of germanium added to the catalyst as the treatingagent. Usually, it is believed that a weight range of germanium of fromabout 0.001 to about 1 part by weight germanium per 100 parts by weightof treated cracking catalyst will provide very good results. It appearsmost desirable to maintain a germanium concentration on the catalyst ofbetween about 0.01 to about 0.5 parts by weight of germanium per 100parts by weight of treated cracking catalyst, because compositionshaving germanium concentrations within this range have been tested withexcellent results.

The manner in which the treating agent is contacted with the crackingcatalyst is not critical. The treating agent can be contacted with thecracking catalyst in any manner effective to impart to the crackingcatalyst a passivating concentration of germanium. For example, theagent in finely divided form can be mixed with a cracking catalyst inordinary manner such as by rolling, shaking, stirring or the like.Alternatively, the treating agent can be dissolved or dispersed in asuitable liquid, e.g., water, hydrocarbon or aqueous acid, depending inpart on the particular treating agent used, and the resulting solutionor dispersion can be used to impregnate the cracking catalyst, followedby volatilization of the liquid, or the treating agent can beprecipitated onto the catalyst from a solution of the treating agentfollowed by solvent removal, or, the treating agent can be sprayed ontothe catalyst. Preferably, the treating agent is dissolved or dispersedin the hydrocarbon feedstock used in a fluid catalytic cracking process,in which instance the hydrocarbon feedstock and the treating agentcontact the cracking catalyst at about the same time. Also, if desired,the cracking catalyst can be exposed to the treating agent in vapor formto deposit the agent on the catalyst. Of course, combinations of thesevarious methods can be employed to produce the modified crackingcatalyst of the present invention.

The feedstocks employed in the catalytic cracking process of thisinvention can and generally do contain metal contaminants, for example,nickel, vanadium and iron. The feedstocks include those which can beutilized in catalytic cracking processes to produce gasoline and lightdistillate fractions from heavier hydrocarbon feedstocks. The feedstocksgenerally have an initial boiling point above about 400° F. (204° C.)and include fluids such as gas oils, fuel oils, heavy oils, cycle oils,slurry oils, topped crudes, shale oils, oils from tar sands, oils fromcoal, mixtures of two or more of these, and the like. By "topped crude"is meant those oils which are obtained as the bottoms of a crude oilfractionator. If desired, all or a portion of the feedstock canconstitute an oil from which a portion of the metal content previouslyhas been removed, e.g., by hydrotreating or solvent extraction.

A preferred embodiment of the cracking process of this inventionutilizes a cyclic flow of catalyst from a cracking zone to aregeneration zone. In this process, a hydrocarbon feedstock containingcontaminating metals, for example, nickel, vanadium and iron, iscontacted in a cracking zone under cracking conditions and in theabsence of added hydrogen with a fluidized cracking catalyst which hasbeen treated in accordance with the invention; a cracked product isobtained and recovered; the cracking catalyst is passed from thecracking zone into a regeneration zone; and in the regeneration zone thecracking catalyst is regenerated by being contacted with a freeoxygen-containing gas, preferably air. The coke that has been built upduring the cracking process is thereby at least partially burned off thecatalyst. The regenerated cracking catalyst is reintroduced into thecracking zone for contact with additional feedstock.

Furthermore, it is preferred in carrying out the cracking process ofthis invention to replace a fraction of the total cracking catalyst byunused cracking catalyst continuously or intermittently. Generally,about 0.5 to about 7 weight percent of the total cracking catalyst isreplaced daily by a fresh cracking catalyst. The actual quantity of thecatalyst replaced depends in part upon the nature of the feedstock used.Where the feedstock used in heavily laden with contaminants, a largeramount of cracking catalyst is replaced daily, optimally so that theamount of catalyst withdrawn daily has an amount of contaminantsdeposited thereon which is equal to the amount of contaminants newlydeposited daily on the catalyst inventory; i.e., a sufficient amount ofcatalyst inventory is replaced daily to maintain the amounts ofcontaminants on the catalyst at an equilibrium level. The make-upquantity of cracking catalyst can be added at any location in theprocess. Preferably, however, the cracking catalyst that is make-upcatalyst is introduced into the regeneration zone in the cyclic crackingprocess.

Also, it is to be understood that the used cracking catalyst coming fromthe cracking zone, before introduction into the regenerator, is strippedof essentially all entrained liquid or gaseous hydrocarbons. Similarly,the regenerated catalyst can be stripped of any entrained oxygen beforeit reenters the cracking zone. The stripping is generally done withsteam.

The specific conditions in the cracking zone and in the regenerationzone are not critical and depend upon several parameters, such as thefeedstock used, the catalyst used, and the results desired. Preferablyand most commonly, the cracking and regeneration conditions are withinthe following ranges:

    ______________________________________                                        Cracking Zone                                                                 Temperature:      800-1200° F. (427°-649° C.)            Cracking Time:    1-40 seconds                                                Pressure:         Subatmospheric to 3000 psig                                 Catalyst:oil ratio                                                                              3:1 to 30:1, by weight                                      Regeneration Zone                                                             Temperature:      1000°-1500° F. (538°-816°                         C.)                                                         Catalyst Regeneration Time:                                                                     2-40 minutes                                                Pressure:         Subatmospheric to 3000 psig                                 Regeneration Air at 60° F.                                                               100-250 ft.sup.3 /lb coke                                   (16° C.) and 1 atmosphere:                                                               (6.2-15.6 m.sup.3 /kg coke)                                 ______________________________________                                    

Advantageously, and in accordance with a preferred embodiment of thisinvention, the treating agent selected from germanium and germaniumcompounds is added to the feedstock entering the cracking zone to form asolution or mixture which contacts the contaminated fluidized crackingcatalyst in the cracking zone. Typically, this feedstock will containone or more of the metals within the ranges shown in Table I:

                  TABLE I                                                         ______________________________________                                                         Metal Content of                                             Metal            Feedstock, ppm.sup.(1)                                       ______________________________________                                        Nickel           0.02 to 100                                                  Vanadium         0.02 to 500                                                  Iron             0.02 to 500                                                  Total effective metals                                                                            0.2 to 1400.sup.(2)                                       ______________________________________                                         .sup.(1) The ppm metal content refers to the feedstock as used. As used i     this table and throughout the specification, ppm means parts per million,     by weight.                                                                    .sup.(2) Total effective metals in this table refer to the sum of the         vanadium, iron and 4 times the nickel contents in the feedstock that are      effective in contaminating the catalyst; the total metals content can be      determined in accordance with methods well known in the art, e.g., by         atomic absorption spectroscopy.                                          

Most preferably, the germanium-containing treating agent is meteredcontinuously into the catalytic cracker along with the feedstock at atleast a rate which is related to the amounts of contaminants in thefeedstock set forth in Table II:

                  TABLE II                                                        ______________________________________                                        Total Effective Metals                                                                       Germanium Concentration                                        in Feedstock (ppm).sup.(1)                                                                   in Feedstock (ppm)                                             ______________________________________                                        <1-40          0.005-20                                                        40-100        0.2-50                                                         100-200        0.5-100                                                        200-300        1.0-200                                                        300-800        2.0-500                                                        ______________________________________                                         .sup.(1) Fe(ppm) + V(ppm) + 4Ni(ppm)                                     

One of the most important embodiments of this invention resides in aheavy oil cracking process. Most known commercial heavy oil crackingprocesses are capable of cracking heavy oils having a metals content ofup to 100 ppm of total effective metals as defined above but with onlyeconomically marginal results obtained with oils having 50 to 100 ppm oftotal effective metals. This is because the catalyst becomes rapidlydeactivated from accumulated contaminants. In accordance with thisinvention, heavy oils with a total metals content of about 50 to 100 ppmand even those of about 100 to 200 ppm and above of total metals can becracked in a cracking process by utilizing the treated cracking catalystto yield gasoline and other fuels and fuel blending components. Thus,heavy oils with total metals contents of from 100 to 300 ppm that couldnot be directly used for fuel production in most known processes, and inparticular for gasoline or higher-boiling hydrocarbon fuels production,in accordance with this invention can be cracked to yield gasoline andhigher-boiling hydrocarbon fuels such as kerosene, diesel fuel andburning oils.

The invention will be still more fully understood from the followingexample, which is intended to illustrate a preferred embodiment of theinvention but not to limit the scope thereof.

EXAMPLE I

A commercial cracking catalyst comprising amorphous silica-aluminaassociated with zeolitic material, which had been used in a commercialcracking unit and subsequently subjected to regeneration in thelaboratory, was employed in tests which demonstrated the advantageoususe of germanium in improving a metals-contaminated used crackingcatalyst. The catalyst contained in excess of 20,000 ppm vanadiumequivalents of nickel and vanadium. Properties of the used crackingcatalyst prior to regeneration in the laboratory are shown in Table III.

                  TABLE III                                                       ______________________________________                                        Surface area, m.sup.2 /g                                                                         74.3                                                       Pore volume, mL/g  0.29                                                       Composition, weight %                                                         Aluminum           21.7                                                       Silicon            24.6                                                       Nickel             0.38                                                       Vanadium           0.60                                                       Iron               0.90                                                       Cerium             0.40                                                       Sodium             0.39                                                       Carbon             0.06                                                       ______________________________________                                    

This catalyst contained 21,200 vanadium equivalents.

The used commercial cracking catalyst having the properties shown inTable III was then subjected to regeneration in the laboratory byheating the catalyst while fluidized with air to 1200° F. (649° C.) andmaintaining it at that temperature for about 30 minutes while fluidizedwith air. The catalyst was then cooled to room temperature (about 25°C.) while fluidized with nitrogen, and the resulting regeneratedcatalyst, herein designated as catalyst O, was employed as shown below.

A portion of catalyst O was used in the preparation of a catalystcomposition containing 0.5 part by weight germanium per 100 parts byweight catalyst O. This was done by mixing 35 g of catalyst O with asolution of 0.92 g tetraphenylgermanium in 35 mL of cyclohexane. Themixture was then dried by heating to 500° F. (260° C.) on a hot plate.

The above catalyst comprising germanium was conditioned in the followingmanner. The catalyst was placed in a laboratory-sized, confined fluidbed, quartz reactor and heated from room temperature (about 25° C.) to900° F. (482° C.) while fluidized with nitrogen, then heated from 900°F. (482° C.) to 1200° F. (649° C.) while fluidized with hydrogen. Whilemaintained at about 1200° F. (649° C.), the catalyst was then fluidizedwith nitrogen for 5 minutes, followed by fluidization with air for 15minutes. The catalyst was then aged through 10 cycles, each cycle beingconducted in the following manner. The catalyst was cooled from 1200° F.(649° C.) to about 900° F. (482° C.) during 0.5 minute while fluidizedwith air, then fluidized with nitrogen while maintained at approximately900° F. (482° C.) for about 1 minute, then heated to 1200° F. (649° C.)during 2 minutes while fluidized with nitrogen and hydrogen, thenmaintained at 1200° F. (649° C.) for 1 minute while fluidized withnitrogen, and then maintained at 1200° F. (649° C.) for 10 minutes whilefluidized with air. After these 10 aging cycles the catalyst was cooledto room temperature (about 25° C.) while fluidized with nitrogen toprovide a catalyst herein designated as catalyst A.

Catalysts O and A were evaluated in two series of cracking-regenerationcycles, using approximately 34-35 g of catalyst as a confined fluid bedin a quartz reactor and employing topped West Texas crude oil as thefeedstock in the cracking step. Properties of the topped West Texascrude oil are shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        API gravity @ 60° F. (16° C.).sup.(1)                                                  21.4                                                   Distillation, °F. (°C.).sup.(2)                                 IBP                    556 (291)                                              10%                    803 (428)                                              20%                    875 (468)                                              30%                    929 (498)                                              40%                    982 (528)                                              50%                    1031 (555)                                             Carbon residue, Ramsbottom, wt. %.sup.(3)                                                            5.5                                                    Elemental analysis                                                            S, wt. %               1.2                                                    Ni, ppm                5.24                                                   V, ppm                 5.29                                                   Fe, ppm                29                                                     Pour point, °F. (°C.).sup.(4)                                                          63 (17)                                                Kinematic viscosity, cSt.sup.(5)                                              @ 180° F. (82° C.)                                                                     56.5                                                   @ 210° F. (99° C.)                                                                     32.1                                                   Refractive index @ 67° C..sup.(6)                                                             1.5                                                    ______________________________________                                         .sup.(1) ASTM D 28767                                                         .sup.(2) ASTM D 116061                                                        .sup.(3) ASTM D 52464                                                         .sup.(4) ASTM D 9766                                                          .sup.(5) ASTM D 44565                                                         .sup.(6) ASTM D 174762                                                   

In each cracking-regeneration cycle the cracking step was carried out at950° F. (510° C.) and about atmospheric pressure for 0.5 minute, and theregeneration step was conducted at about 1200° F. (649° C.) and aboutatmospheric pressure for approximately 0.5 hour using fluidizing air,the reactor being purged with nitrogen before and after each crackingstep. Catalyst A was evaluated at catalyst:oil weight ratios of 7.32 and7.55. Catalyst O was evaluated under various conditions, includingvarying catalyst:oil weight ratios. Among the many tests carried out,the three tests with catalyst O most comparable to those conducted withcatalyst A were carried out at catalyst:oil weight ratios of 6.81, 7.70and 7.67, ratios which straddle those used in the evaluation of catalystA. Except for the variation in catalyst:oil weight ratios as noted,these five tests of the two catalysts with or without the use of agermanium treating agent were conducted under comparable conditions.Results of these five evaluations are summarized in Table V.

                                      TABLE V                                     __________________________________________________________________________                             Yield                    Selectivity                           Catalyst.sup.2 :Oil.sup.3                                                            Conversion,                                                                           Coke,   H.sub.2, SCF/bbl                                                                       Gasoline.sup.4,                                                                       to Gasoline,                Run No.                                                                            Catalyst                                                                           Weight Ratio                                                                         Vol % of Feed                                                                         Wt % of Feed                                                                          Feed Converted                                                                         Vol % of Feed                                                                         Vol %                       __________________________________________________________________________    1    0    6.81   72.5    17.0    789      51.5    71.0                        2    0    7.70   74.9    17.7    896      54.7    73.0                        3    0    7.67   74.7    15.6    828      52.2    69.8                        .sup. 4.sup.2                                                                      A    7.32   75.0    14.1    586      63.4    84.5                        .sup. 5.sup.1                                                                      A    7.55   79.6    14.7    592      65.8    82.7                        __________________________________________________________________________     .sup.1 0.5 wt. % Ge via impregnation with tetraphenyl germanium               .sup.2 21,200 vanadium equivalents                                            .sup.3 21.4° A.P.I.                                                    .sup.4 Gasoline is that portion of feed converted to C.sub.5 and higher       hydrocarbons boiling at a temperature up to 410° F. (210°       C.) at atmospheric pressure.                                             

As shown in Table V, catalyst A, which contained 0.5 part by weightgermanium per 100 parts by weight cracking catalyst used in itspreparation, was more active, produced less coke and less hydrogen, andprovided more gasoline than catalyst O, to which no germanium had beenadded. Table V also shows that the selectivity to gasoline wasapproximately 15 percent higher with catalyst A than with catalyst O.

EXAMPLE II

To a slurry containing 25.24 g (0.10 mole) of potassiumdi-n-propyl-phosphorodithioate in benzene a solution of 5.36 g (0.025mole) of germanium tetrachloride in benzene was added dropwise, atambient temperature, with stirring. Stirring continued for an hour, thenthe mixture was heated to reflux temperature and held there for about 2hours. After cooling, insoluble potassium chloride formed by the doubledecomposition reaction was removed from the solvent containing productby filtration through a bed of diatomaceous earth filter aid. Solventwas then removed from the product on a rotary evaporator.

The product, germanium tetrakis(di-n-propylphosphorodithioate) wascalculated to be of the composition C₂₄ H₅₆ O₈ P₄ S₈ Ge. The results ofelemental analysis of the product and comparison with the calculatedformula, are given in Table VI.

                  TABLE VI                                                        ______________________________________                                        Element       Calculated   Found                                              ______________________________________                                        C             31.14 wt. %  32.19 wt. %                                        H              6.10         6.44                                              P             13.38        13.2                                               S             27.71        25.9                                               Ge             7.84         7.5                                               ______________________________________                                    

Samples of the passivating agent characterized by Table VI were employedto treat samples of catalyst O to impart to the samples germaniumconcentrations of 0.01, 0.05, 0.10 and 0.20 weight percent. This wasaccomplished by mixing with 40 g samples of catalyst O solutions of 40mL of cyclohexane containing 0.051 g, 0.255 g, 0.51 g and 1.02 g of theabove characterized germanium tetrakis(di-n-propylphosphorodithioate)and removal of the solvent by heating the mixture on a hot plate. Thecatalyst samples were then aged as in Example I and employed tocatalytically crack a gas oil feedstock characterized as follows:

                  TABLE VII                                                       ______________________________________                                        API gravity at 60° F.                                                                       25.8                                                     Carbon residue, Ramsbottom                                                                         0.87                                                     Elemental analysis                                                            Sulfur               0.40                                                     Nitrogen             0.07                                                     ______________________________________                                    

The cracking and regeneration runs were conducted under the conditionsset forth in Example I. Results of some runs with these catalysts areshown in Table VIII.

                                      TABLE VIII                                  __________________________________________________________________________                 Cat.sup.2 /Oil.sup.3                                                                Conversion                                                                           Yields                     Selectivity to           Run No                                                                              Additive.sup.1                                                                       Ratio (Vol. % feed)                                                                        Gasoline (Vol. %)                                                                       Coke (wt. %)                                                                         H.sub.2 (SCF/bbl                                                                        Gasoline (%              __________________________________________________________________________                                                         Conv)                    1     None   7.70  64.4   53.79     7.95   631       83.6                     2     0.01 wt % Ge                                                                         7.70  66.0   55.08     7.20   509       83.6                     3     0.05 wt % Ge                                                                         7.69  66.3   57.83     6.90   435       86.3                     4     0.10 wt % Ge                                                                         7.70  65.7   58.1      6.50   385       88.6                     5     0.20 wt % Ge                                                                         7.68  64.6   56.74     6.40   408       87.8                     __________________________________________________________________________     .sup.1 germanium tetrakis (din-propylphosphorodithioate)                      .sup.2 21,200 vanadium equivalents                                            .sup.3 25.8° A.P.I.                                               

In addition to the runs in Table VIII, additional runs with thesecatalysts were made at other catalyst/oil ratios, to vary conversion.From these runs (never fewer than five per catalyst), curves ofconversion vs. catalyst/oil ratio were calculated, and the data in TableIX were obtained from the smoothed curves at constant conversion.

The incorporation of germanium into the cracking catalyst at levels offrom 0.01 to 0.20 percent by weight was effective to increase itsactivity for cracking and its selectivity for gasoline production, andto decrease the selectivity of the cracking catalyst for hydrogenproduction and coke production. For the cracking catalyst tested, whichcontained over 20,000 ppm vanadium equivalents of nickel and vanadium,maximal benefit was observed at germanium concentrations of between 0.05and 0.20 percent by weight, a weight ratio of elemental germanium tocontaminants on the catalyst between about 1:10 to about 1:40.

                                      TABLE IX                                    __________________________________________________________________________                 Cat.sup.2 /Oil.sup.3                                                                Conversion                                                                           Yields                     Selectivity to           Run No                                                                              Additive.sup.1                                                                       Ratio (Vol. % feed)                                                                        Gasoline (Vol %)                                                                        Coke (wt. %)                                                                         H.sub.2 (SCF/bbl                                                                        Gasoline (%              __________________________________________________________________________                                                         Conv.)                   1     None   7.7   64      53.79    7.95   631       86.0                     2     0.01 wt. % Ge                                                                        7.0   64      53.85    6.83   493       84.1                     3     0.05 wt. % Ge                                                                        6.9   64     56.5      6.4    423       88.5                     4     0.10 wt. % Ge                                                                        7.1   64     57.5      6.10   378       89.9                     5     0.20 wt. % Ge                                                                         7.85 64     55.0      6.61   419       86.0                     __________________________________________________________________________     .sup.1 Germanium tetrakis (din-propylphosphorodithioate)                      .sup.2 21,200 vanadium equivalents                                            .sup.3 25.8° A.P.I.                                               

EXAMPLE III

Five different catalysts were prepared by treating 40 grams of theequilibrium cracking catalyst characterized in Example I with solutionsof antimony and/or germanium salts of di-n-propylphosphorodithioic acidin 40 mL cyclohexane. The salt solutions were mixed with samples of thecracking catalyst and the solvent removed by evaporation. The treatedcracking catalyst samples containing the desired levels of germaniumand/or antimony were then aged as described in Example I and employed tocrack the gas oil feedstock characterized in Example II under theconditions described in Example I at 510° C. Some results of these runsare set forth in Table X.

Examination of the data presented in Table X reveals that germanium isabout as good as antimony in reducing the undesirable cracking behaviorof metals contaminated zeolite containing cracking catalysts.Interestingly, it appears that germanium and antimony cooperateadvantageously when present on the cracking catalyst in a weight ratioof about 1:10 to increase gasoline production and decrease hydrogenproduction. It is thus believed that germanium is effective to promotethe passivation effects of antimony when present on the crackingcatalyst in a weight ratio of germanium to antimony between about 1:100to about 1:1.

                                      TABLE X                                     __________________________________________________________________________                   Cat.sup.2 /Oil.sup.3                                                               Conversion                                                                           Yields                    Selectivity to           Run No                                                                             Additive.sup.1                                                                          Ratio                                                                              (Vol. % feed)                                                                        Gasoline (Vol. %)                                                                       Coke (wt. %)                                                                         H.sub.2 (SCF/bbl                                                                       Gasoline (%              __________________________________________________________________________                                                         Conv)                    1    None      7.7  64.3   53.6      7.8    630      83.3                     2    0 Ge + 0.1 Sb                                                                           7.7  64.8   55.0      6.0    410      84.9                     3    0.01 Ge + 0.1 Sb                                                                        7.7  65.5   57.0      6.4    360      87.1                     4    0.05 Ge + 0.05 Sb                                                                       7.7  64.5   54.8      6.7    375      85.0                     5    0.1 Ge + 0.01 Sb                                                                        7.7  64.0   55.0      6.3    410      86.0                     6    0.1 Ge + 0 Sb                                                                           7.7  65.0   57.1      6.5    380      89.5                     __________________________________________________________________________     .sup.1 Ge as Ge ((C.sub.3 H.sub.7 O).sub.2 PS.sub.2).sub.4 ; Sb as Sb         ((C.sub.3 H.sub.7 O).sub.2 PS.sub.2).sub.3                                    .sup.2 21,200 vanadium equivalents                                            .sup.3 25.8° A.P.I.                                               

What is claimed is:
 1. A composition represented by the formula ##STR4##wherein R is alkyl having from 1 to about 6 carbon atoms.
 2. Acomposition as in claim 1 wherein R is n-propyl.